Jet injectors employing unit dose ampuls of glass are known to the art as seen from U.S. Pat. No. 3,688,765. The prior art ampuls are unsatisfactory for a number of reasons. They do not have adequate provisions for keeping the ampul sterile until immediately before the inoculation is to be carried out. They have no provision for preventing the inoculator from becoming contaminated by contact with the flesh of the patient which is wetted with the medicament being administered. In addition, the prior art ampuls are awkward to secure to the injector since they do not have any securing means attached thereto but rely on securing means on the injector which must be removed before the ampul is inserted in the injector.